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(11) | EP 0 426 632 A3 |
(12) | EUROPEAN PATENT APPLICATION |
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(54) | Impact motor |
(57) An impact motor comprises a housing (10) with a cylinder (11) therein, in which
a reciprocating drive piston (40) via a gas cushion in a working chamber (44) of said
cylinder (11) repeatedly drives a hammer piston (15) to impact on and to return from
the neck (17) of a tool (20) carried by the machine housing (10). A piston groove
(68) is provided adjacent to the front face (70) of the drive piston (40) and the
peripheral part of said face (70) is rounded (71) towards said groove (68). A piston
ring (41) is of steel having a temperature expansion coefficient substantially equal
to the cylinder's (11) and is ground circumferentially to have a close sliding and
sealing fit in the cylinder (11). The rounded (71) drive piston face (70) is adapted
to the inner diameter of said ring (41) so as to permit the ring (41) to be forced
into said groove (68) undeformed to ride on a elastically centering O-ring (69) of
heat resistant rubber. The hammer piston (15) can alternatively have a similarly arranged
steel or heat resistant plastics material piston ring (16) therearound or be machined
to a sliding and sealing fit in the cylinder (11). |